Process for cracking hydrocarbon oils and producing ethylene



L. C. HUFF `June 12, 1934.

PROCESS FOR CRACKING HYDROCARBON OILS AND PRODUCING ETHYLENE original Filed sept. 5, '192e im Q Patented VJune 12, 1934 PROCESS FOR CRACKING HYDROCARBON OILS AND PRODUCING ETHYLENE Lyman C. Huff, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of South Dakota Continuation Lof application Serial No. 133,467,

September 3, 1926. This application September 14, 1931, Serial No. 562,747

Claims.

This application is a continuation of my application Serial No. 133,467, filedSeptember 3, 1926. My invention relates'to an improved process for cracking hydrocarbon oils Vand one in which ethylene may be produced as an incident to the practice of the process.- It has heretofore been the practice to subject heavy hydrocarbons to cracking either in the liquid phase, the vapor phase or a combined liquid and vapor phase process for the purpose of producing lighter hydrocarbons. My invention. relates to a combined liquid phase and vapor phase process and contemplates an improvement in what is known in the art as a continuous process.

More specifically, my invention contemplates l the superheating of vapors from which the heavier constituents have been removed by condensation and the subjection of such vapors to further reaction whereby a more efficient cracking operation is effected and substantial quantities of ethyl- "39 shown in side elevation an apparatus suitable for practicing the invention. I

For the purposes y'of clearness the operation of the process will be described in connection with `the apparatus illustrated in the drawing. rIt is to be understood, however, that other forms of apparatus may be employed;

'I'he apparatus comprises generally a furnace A, oil heating coil B, a vapor superheating coil C, a/primary reaction chamber D, preferably unheated for the heated oil, a primary dephlegmator E for the vapors issuing from the chamber D, a secondary reaction chamber F, preferably unheated for the superheated vapors from the coil C, a secondary dephlegmator G in which vapors issuing from the chamber F are treated, a final condenser H and a receiver I.

In operation the oil is supplied to the coll B through the line 1, pump 2 and charging line 3. The oil may be either directly passed to the coil B or by suitably controlling the valves 4, 5, 7 and 9 the oil or a. portion thereof may be vpassed through the line 6 and either passed through the closed conduit 8 in the dephlegmator G or through the by-passing line l() controlled by the valve 9 to the line 11 and thence delivered to the primary (Cl. 26o- 170) dephlegmator E through the spray 12, or by suitably regulating the valves 13 and 14 the oil flowing through the line l1 may be passed through the closed conduit 15 disposed within the primary dephlegmator E and thence passed by way of the line 16 and valve 17 to the charging line 3.

It will be understood that when oil is delivered to the primary dephlegmator E through the spray 12, the unvaporized portions of this oil together with reflux condensate separated from the vapors in the dephlegmator E will be passed via the line 18 and valve 19 to the charging line 3. In the event that differential pressures are employed, or in the event that the gravity head of the liquid is insufficient to supply the same to the charging 76 line 3, the charging oil and reflux oil from the dephlegmator E maybe, by suitably controlling valves 19, 20 and 21 forced under a mechanical pressure imposed by the pump 22 into the charging line 3.

The oil passed through the heating coil B is raised toa cracking temperature therein and is then delivered by Way of the line 23 controlled by the 'valve 24 to the primary reaction chamber D wherein substantial conversion of the oil and vaporization thereof takes place. Unvaporized residue accumulating in the chamber D can be withdrawn therefrom through the lines 25 controlled by the valves 26. The vapors issuing from the chamber D arevcaused to pass through the B5 line 27 controlled by the valve 28 to the primary dephlegmator E wherein the heavier or insufficiently cracked fractions of'the vapors are condensed forming reflux condensate which accumulates in the bottom of the dephlegmator E, and is removed therefrom through the line 18 as above described.

The uncondensed vapors leave the dephlegmator E through the line 29 controlled by the valve 30 and in the preferred operation of the process these g5 vapors are passed via the line 32 controlled by the valve 31 to the vapor superheating coil C positioned in the furnace A. It is to be noted that this coil C is nested intermediate the upper and lower `rows of the tubes forming the coil B. This per- C. Furthermore steam may be passed through the coil C to prevent burning out of vthis coil in the event that it is not employed for superheating oil vapors.

Any heavy hydrocarbons resulting from the superheatin'g and reaction of the vapors will accumulate in the secondary reaction chamber F and may, if in liquid form, be removed therefrom throughthe lines 37 controlled by the valves 38. The vaporous products leave the secondary reacf tion chamber through the line 39 controlled by of the secondary dephlegmator G. The vapors from the heat interchanger 41 pass through the line 42 into the dephlegmator G. In the event that it is not desired to subject the vapors issuing lfrom the secondary reaction chamber li'4 to additional dephlegmation these vapors may be passed directly to the condenser H- through the line 43' controlled by the valve 44.. When, however, the vapors are delivered to the dephlegmator G they pass therefrom through the line 45 controlled by the valve 46 to the nal condenser H from which the distillate and gases flow through the line 4'7 controlled by suitable valve 47' to the receiver Il which is of conventional form being provided with a .valve controlled distillate drawoll line 48 and a valve controlled gas outlet line 49. A secondary distillate drawoff line 50 controlled by valve 51 is provided which communicates with the pump 52 by which distillate collectingin the receiver I may be forced Via the line 53 controlled by the valve 54 into the top of the secondary dephlegmator G. By closingthe valve 54 and opening the valve 55, this distillate may be passed through the line 56 and united with reflux condensate from the secondary dephlegmator in the line 60,v these substances being charged by the pump 5'7 and line 58 to the primary dephlegmator E where they are introducedthrough the spray 59. The reflux condensate from the secondary dephlegmator which iswithdrawn from the line 60 may be passed tothe primary dephlegmator E as above described, or wholly or in part withdrawn from the process and sent to suitable storage e through the line 62 by suitably controlling valves 61 and 63.

It may be desirable at some times to eliminate the vapor treating system from the process and to directly condense the vapors issuing from the primary dephlegmator E. To permit of such an operation I provide the line 64 controlled by the valve 65 for conveying vapors issuing from the primary dephlegmatorE through the line 29 to the nal condenser H. It will be understood, of course, that when these vapors are being passed to the final condenser H, the valve 31 in the line 32 will be closed. While they superheating of vapors evolved in the cracking operation has been suggested, it has never heretofore provided practical because of the abundance of carbon present in the vapors which is separated therefrom and collects as a flint like coating on the'walls of the vapor superheating zone. It Will be seen that in my process all of the heavier constituents which contain the greatest percentage of carbon are separated from the vapors prior to the superheating of the vapor, and that I thereby eliminate the difllculties due to excessive carbon formation. I

nasales furthermore provide a time element for the reaction of the superheated vapors by introducing these vapors to the enlarged reaction chamber F.

The process may be carried out by maintaining uniform pressure conditions throughout all of the 'separate zones thereof. However, it is desirable to maintain a somewhat lower pressure on the vapor treating portion of the system, that is the heating coil C, reaction chamber Fand associated elements, than is maintained in the oil treating portion of the system. One particular advantage obtained from such an operation is that the pressure maintained in the oil treating system is suflcient to convey the vapors through the vapor treating portion of the system. It is to be noted, however, that the introduction of steam through the line 35 enables the operation of the process when uniform pressures are maintained. It will be understood that the ethylene produced by the process will be taken off from the receiver I with the gases and recovered therefrom.

Because of the variations in the character of hydrocarbon oils of different characteristics and from different sources, the operating conditions maintained in the process must necessarily be varied and to this end the process is extremely exible. Good results may be obtained, however,'

when treating a fuel oil by subjecting the same in the coil B to a temperature of from 800 to 850 F., and by maintaining a pressure in the liquid treating portion of the system of from 135 to 150 pounds per square inch.

Heating of the vapors in the coil C can be controlled by various means. For example, the rate of cooling in the dephlegmator E will, of course, govern the quantity of vapor passed through the coil C as Well as the quantity ofv oil flowing through the coil B. By suitably controlling the temperature in the dephlegmator E, the desired superheating of the vapors in the coil C can be obtained. The degree of heat imparted to these vapors will, of course, be dependent upon the character of the oil treated and the character of the product obtained. A skilled operator can by observing the characteristics of the distillate and gases produced determine the best operating temperature for the vapors from a particular oil and by suitably controlling the conditions of the clephlegmator maintain such temperature.

From the foregoing, it willbe seen that I have devised an improved continuous process for the cracking of hydrocarbon oil and the production of ethylene which may be incorporated in many of the existing continuous cracking processes without substantial change in the present installation.

. What I claim as my invention is:

1. A process for cracking heavy hydrocarbon oil and .for producing ethylene which comprises subjecting the oil to cracking conditions of tem-v perature and pressure and separating the same into vapors and residue, dephlegmating the vapors to condense heavier and insufficiently cracked fractions thereof while retaining the normally condensible light cracked products in vapor form, returning resultant reux condensate to the cracking step for retreatment in the process, heating such light cracked products uncondensed by said dephlegmation to an ethylene-producing temperature While in vapor phase, cooling the thus heated vapors to condense normally liquid constituents thereof, and separating the resultant condensate from the ethylene-containing gases.

2. A process for cracking Vheavy hydrocarbon oil and for producing ethylene which comprises Locales subjecting the oil to cracking conditions of teinperature andpressure and separating the same into ,vaporsl `and residue, dephlegmating the vapors to condense heavier and insufflciently cracked 5 fractions thereof while retaining the normally condensible light cracked products in vapor form, returning resultant reflux condensate tot the cracking step for retreatment in the process, heating the dephlegmated vapors, prior to condensation thereof, and reacting the same at an ethylene-producing temperature in admixture with steam, cooling the thus heated vapors to condense normally liquid constituents thereof, and sep,- arating the resultant condensate from the ethylene-containing gases. c y 3. A process for cracking heavy hydrocarbo oil .and for producing ethylene which comprises subjecting the oil to cracking conditions of temperature and pressure and separating the same into vapors and residue, dephlegmating the vapors to condense heavier and insufciently cracked fractions thereof and returning resultant reflux condensate to the cracking step for retreatment in the process, heating the dephlegmated vapors, prior to condensation' thereof, and reacting the same at an ethylene-producing temperature, dephlegmating the thus heated vapors independently of the first-mentioned vapors thereby forming secondary reflux condensate, introducing such secondary reux condensateinto contact with said first-mentioned vapors undergoing dephlegmation to assist the dephlegmation thereof and returning unvaporized portions of thesecondary reux condensate to the cracking step in admixture with the first-mentioned reflux condensate, further cooling the still uncondensed vapors to condense normally liquid constituents thereof, and separating the ethylene-containing gases from the resultant condensate. l

4.,A hydrocarbon oilI cracking process which comprises subjecting the ollto cracking conditions of temperature and pressure in a cracking zone, removing evolved vapors and denlesmating the same in a primary dephlegmating zone w condense heavier fractions .thereof as primary reux condensate, passing the dephlegmated vapors to a vapor phase conversion zone and treating the same therein at an ethylene-producing tempera.- ture under lower pressure than is maintained `on theoll in the cracking zone, dephlegmating the thus treated vapors in a second dephlegmating zone thereby forming secondary reflux condensate, combining at least a portion of said secondary reflux condensate with theprimary reflux condensate and supplying the resultant mixture under pressure to the cracking zone, cooling the vapor-gas mixture from the secondLdephlegmating zone to condense normally liquid constituents thereof, and separating'the ethylene-containing gases from the resultant condensate.

5. A hydrocarbon oil cracking process which comprises subjecting the oil to cracking conditions of temperature and pressure in a cracking zone, removing .evolved vapors and dephlegmating the same in a primary dephlegmating zone to condense heavier fractions thereof as primary reflux condensate while retaining the normally condensible light cracked products in vapor form, passing light cracked products uncondensed by said dephlegmation to a vapor phase conversion zone and heating the same therein at an ethylene-producing temperature under lower pressure than is maintained on the oil in the cracking zone, dephlegmating the vapors from said vapor phase conversion zone in a second dephlegmating zone thereby forming secondary reflux condensate, combining at least a portionof said secondary reux condensate with the primary reflux condensate and supplying the resultant mixture under pressure to the cracking zone, cooling the vapor-gas mixture from the second dephlegmating zone to condense normally liquid constituents thereof, and separating the ethylene-con- 'taining gases from the resultant condensate.

LYMAN C. HUFF. 

